This change modifies sync_motion to sync the camera for all it's relevant motion steps, not just for relative times -1, 0, and 1.

rB78c2063685cb adds the ability to set motion blur steps for cameras, and initializes the necessary data structures to store the camera transforms for various time steps. However, the camera is never synced at those time steps, so the transforms remain the default (whatever the transform is at relative time 0).

This change appears to fix T72889. Here are the resulting fixed renders for the debug file in T72889: